This is how I feel about SMS, and phone numbers too for that matter. They're still around for historical reasons, but if we started anew, I can't imagine we would build out that infrastructure separately from the greater internet, and if we would have, I can't think of a reason why.
The spec also handles video calls, conference calls, sending/receiving money, and just about anything else a modern messenger does.
It just lacked E2EE for the longest time, which makes sense when you consider that the police and secret service have their tendrils in the standards body that publishes the spec.
Synchronisation is not part of the problem it's trying to solve (sending messages between devices), the same way SMS and MMS don't, so that's up to the apps implementing the protocol.
E2EE has been added very recently (https://www.gsma.com/solutions-and-impact/technologies/netwo... came out a few months ago), and post-quantum encryption is still being developed. It uses standard MLS (RFC 9420) for messaging, so verification will have to be implemented however normal MLS implementations do it. I don't know if there's a standardised way to do it, I haven't fully read the most recent RCS spec yet.
I oversimplified RCS somewhat, it's not just HTTP wrapped in carrier stuff. It's also SIP, SDP, XML, OIDC, RTP, and JSON wrapped in carrier stuff. Still, page 428 of the second link shows an example of a POST request that you can make after combining all of the tidbits of specification that came before it, and that's where the simple JSON+XML shine through the stack of protocols that are tasked with delivering it. The E2EE layer is basically just sending base64'd encrypted messages over that same interface.
Apple, Google, and Samsung can synchronize SMS messages through their cloud services, so the same also goes for RCS. For more privacy-oriented folk, KDE Connect can also offer SMS messaging to the desktop by synchronising locally with a connected phone.
I still hope for a protocol to win out that's not tied to one party.
Not to mention that the choice isn't really between your carrier and Meta, but rather Google and Meta, since most people on Android end up just using Google servers for RCS, and that choice is much more of a toss-up.
We're stuck with iMessage, which Apple is actively hostile towards non-users. Even for me, who had an iPhone, it was a royal pain in the ass. What do you mean I can't see my messages online? I need a Mac? Are you fucking kidding me? I'm a paying customer, why am I being nickled and dimed?
That, and then SMS MMS. Which are so unbelievably bad they're basically worthless.
I shouldnt have to spend 2.5 thousand dollars to get an acceptable messaging experience. I shouldn't. RCS isn't really helping, but the situation is absolutely NOT for the better IMO.
It's patently ridiculous to trust the Signal Foundation more than phone carriers? I wasn't aware that AT&T and T-Mobile are run for the benefit of humanity.
Any app that implements RCS is run by gigantic corporations, most of which I'd argue are closer to the US government than even Meta, it's not obvious to me where the ridicule comes in.